Many intestinal disorders result directly or indirectly from imbalances in finely tuned mechanisms of fluid balance in the intestinal tract, which is responsible for nutrient, electrolyte and fluid absorption, as well as the secretion of waste, excess electrolytes and fluid. The secretion and absorption run in parallel so that homeostasis is maintained. This balance is critical for preventing diarrhea and constipation, as well as malabsorption and malassimilation disorders.
Worldwide, diarrhea claims 3-5 million lives annually, mostly those of infants. Adequate fluid replacement could have prevented almost all of these deaths. Although its incidence is much lower in the more affluent nations, diarrhea remains one of the two most common reasons for visits to pediatric emergency departments and is also common among the elderly. Similar to diarrhea and enteric infections in patients with AIDS, diarrhea and enteric infections in children are associated with profound disruption of the intestinal absorptive surface, malnutrition and long term consequences, such as long-term impairments in growth and cognitive development in young children, and malabsorption of antiretroviral drugs in patients with AIDS. Diarrhea is among the most frequent health problems encountered by travelers. Up to 40% of short-term visitors to developing countries and up to 70% of long-term travelers will experience at least one bout of diarrhea.
While oral rehydration therapy can replace diarrheal losses, it does not facilitate reabsorption of secreted fluid and therefore does not lessen diarrhea. Antibiotics are of limited efficacy in many types of diarrhea and should not be used for treatment of diarrhea of less than five days' duration. Further, many antibiotics can worsen diarrhea. Finally, an effective oral vaccine is not available for epidemic infectious diarrheas.
Constipation is the most common gastrointestinal complaint in the United States and is of particular concern to the elderly. It often remains unrecognized until the patient develops anorectal disorders or diverticular disease. About 2% of the population describes constant or frequent intermittent episodes of constipation. Common treatments include bulk, stimulant, and osmotic laxatives, fecal softeners and lubricants. Chronic use of laxatives, however, is strongly discouraged, especially stimulant laxatives.
Many diseases directly or indirectly alter gastrointestinal physiology in such a manner that normal absorptive mechanisms are compromised, resulting in maldigestion or malabsorption of one or more dietary constituents. Typically, malabsorption can be the failure to absorb specific sugars, fats, proteins, or vitamins, or it can be a general malabsorption of food. Diarrhea, bloating or cramping, failure to thrive, frequent bulky stools, muscle wasting, and a distended abdomen may accompany malabsorption. Prolonged malabsorption can result in malnutrition and vitamin deficiencies. Two basic principles underlie the management of patients with malabsorption: (1) the correction of nutritional deficiencies and (2) when possible, the treatment of causative diseases (e.g., celiac disease, tropical sprue, Whipple's disease, pancreatic insufficiency and short bowel syndrome). However, if the treatment of the underlying disease of malabsorption were challenging due to, e.g., difficulties in diagnosing the disease, patients with malabsorption diseases would benefit from a treatment that addresses the correction of nutritional deficiencies.